EUV (Extreme Ultraviolet) lithography uses radiation in the spectral range between 10 and 15 nm, which is strongly absorbed in solid state bodies and requires reflective optics. A photolithographic mask for employing EUV lithography relies on a multilayer reflector deposited on a polished substrate. Typical multilayer reflectors include 40 or more layer pairs with a molybdenum layer and a silicon layer. It is difficult to produce defect free multilayer reflector masks. On the other hand, defects in the multilayer reflector are difficult to repair. Conventionally, mask blanks can be used despite of defects, when a defined mask pattern can be aligned to the defects in a way such that the defects do not print on a target on which the mask is imaged. Absorber structures defining the mask pattern can be locally reworked to compensate for such defects that otherwise would print on the target. It is desirable to further reduce the costs of EUV lithography.
For these and other reasons, there is a need for the present invention.